Sludge level indicating device for centrifugal separators



1970 CARL-GORAN NILSON 3,494,545

SLUDGE LEVEL INDICATING DEVICF FOR CENTRIFUGAL SEPARATORS Filed Oct. 15, 1968 2 Sheets-Sheet 1 INVENTOR. Mlbhllllaflfl Feb. 10, 1970 CARL-GORAN NILSON I ,5

SLUDGE LEVEL INDICATING DEVICE FOR CENTRIFUGAL SEPARATORS Filed Oct. 15, 1968 2 Sheets-Sheet 2 I V Z 23 Z 1 FIG. 2

' INVENTOR.

till-HM! was BY J d, WMZWW United States Patent 3,494,545 SLUDGE LEVEL INDICATING DEVICE FOR 'CENTRIFUGAL SEPARATORS Carl-Goran Nilson, Tullinge, Sweden, assignor to Alfa- Laval A.B., Tumba, Sweden, a Swedish corporation Filed Oct. 15, 1968, Ser. No. 767,652 Claims priority, application Sweden, Oct. 17, 1967, 14,177/ 67 Int. Cl. B04b 11/00, 11/04 US. Cl. 233-19 5 Claims ABSTRACT OF THE DISCLOSURE THE DISCLOSURE This invention relates to sludge centrifuges and more particularly to an improved arrangement for indicating the sludge level in the sludge-collecting space of the centrifugal rotor.

An arrangement for the above-noted purpose is disclosed in my application Ser. No. 561,890, filed June 30, 1966, now Patent No. 3,410,479. The arrangement there disclosed comprises a channel in the rotor leading radially inward from the sludge space and communicating at its inner end with a stationary duct located outside the rotor; and inserted in this duct are means for sensing a pressure change therein (such as might result from a change in flow) and also means for intermittently generating a pressure pulse in the duct.

In the arrangement disclosed in my said prior application, the pressure sensing means can be influenced in an undesirable manner by certain liquids such as oil, or by a liquid containing impurities such as yeast cells. According to the present invention, this drawback is avoided by inserting the pressure pulse generating means in a connecting chamber through which the inner end of the aforesaid channel in the rotor communicates with the stationary duct in which the pressure sensing means are inserted. This construction allows a gas, such as air, to pass the pressure sensing means in the direction toward the centrifugal rotor, thereby protecting the sensing means against exposure to a liquid which might have an undesirable effect. The new construction is also useful, however, in cases where a liquid not harmful to the pressure sensing means passes the latter.

In principle, it is possible to generate pressure changes in the aforesaid connecting chamber in different ways, for example, by means of separated liquid which, without leaving the interior of the rotor, is supplied to the connecting chamber in successive slugs. According to a preferred embodiment, the pressure pulse generating means comprise a duct opening into the connecting chamber, whereby it is possible to supply the centrifuge rotor from outside with a liquid, whether it be a liquid previously separated I device inserted therein, and the duct in which the pressure pulse generating means are inserted can open into the paring chamber separately from the channel of the paring device.

On the other hand, in cases where the centrifuge is of the type which is maintained completely filled with liquid, the duct in which the pressure generating means are inserted can open into a chamber completely filled with liquid and forming said connecting chamber.

The invention is described more in detail in the following, reference being had to the accompanying drawings in which FIGS. 1 and 2 are vertical sectional views, with parts broken away, of centrifuges embodying two dilferent forms of the invention.

In FIG. 1, a centrifuge rotor 1 is composed of two parts which are held together by a locking ring 2. The rotor wall has sludge outlet openings 3 which are opened and closed in a known manner by a valve piston 4. The rotor is carried and driven by a hollow shaft 5, through the central channel of which the liquid to be separated is supplied to the separating space of the rotor. The liquid enters this space past the lower edge of a distributor 6. The sludge is separated off and forms .a layer 7, whereas purified liquid is led inwards to the center of the rotor through a disc set 8 and is discharged from the center via an overflow outlet 9. The liquid flows from this outlet into a paring chamber 10 and is discharged by a paring disc 11. The latter is connected to an outlet duct 12 for purified liquid.

An indicating pipe 13 is provided in the rotor, and the outer end of this pipe opens into the sludge space. The pipe 13 opens at its inner end into a paring chamber 14, in which a paring disc 15 is provided. This disc is in turn connected to a duct 16 for air supply, and on this duct is mounted a conventional means 17 for sensing and indicating pressure changes (and therefore flow changes) in the duct 16. When the indication is sufiiciently strong, valve 4 is actuated to effect sludge discharge. Furthermore, a means 19 for intermittently supplying liquid is inserted in a duct 18. The supply means 19 may consist of a piston movable in a cylinder, or of a. centrifugal pump having an inlet or outlet which is opened intermittently by means of a valve actuated in any suitable manner, as by means of an electromagnet. The duct 18 can .open at its discharge end either radially inward from the liquid surface in the paring chamber 14 or, as shown by broken lines, within the liquid body in this chamber.

In operation, the paring disc 15 tends to pump liquid into the duct 16, but at the same time air is supplied to the rotor through the same duct. The pressure of the air in duct 16 required to force the liquid out of the paring disc 15 so as to be discharged at the opening of the latter can be measured by the sensing means 17. The measured pressure indicates the position of the liquid level in the paring chamber 14. As long as the opening of the pipe 13 in the sludge space is not clogged by sludge, a quantity of liquid supplied through the duct 18 does not essentially change the position of the liquid level in the paring chamber 14. However, when sludge has clogged this opening of the channel in pipe 13, a liquid quantity supplied through the duct 18 causes a radially inward displacement of the liquid level in the paring chamber 14, whereby the air pressure in the duct 16 rises. The sensing means 17 indicates an increased air pressure, and at an empiricallyestablished increase a sludge discharge can be effected either by hand or automatically.

The embodiment according to FIG. 2 differs from that according to FIG. 1 in that the centrifuge in FIG. 2 operates completely filled with liquid. The paring chamber in the FIG. 1 embodiment is replaced by a chamber 20 completely filled with liquid and into which the duct 16a opens. A duct 21, in which the pulsing means 22 is inserted for generating pressure or flow changes, is hermetically connected to the centrifuge rotor by means of a seal 23. Similarly, the duct 12a is hermetically connected to the rotor by sealing means 24. The separated liquid passes through a chamber 25 on its way from the disc set 8 to the discharge duct 12a.

In the operation of the FIG. 2 arrangement, the means 22 (for example, a periodically opening valve) lets out liquid intermittently from the chamber 20. The air continuously supplied to the chamber 20 through the duct 16a is discharged intermittently through the duct 21. When the opening of the pipe 13 in the sludge space becomes clogged by sludge, this will result in a reduced liquid flow through the pipe 13 and the duct 21, when the means 22 opens for liquid discharge. The sensing means 17 then indicates a reduced pressure; and when the pressure reduction is sufiiciently large, sludge discharge is effected.

I claim:

1. In a sludge centrifuge, the combination of a centrifugal rotor mounted for rotation about an axis and having a separating chamber and a inlet for supplying feed material to said chamber, the rotor forming at its peripheral portion a space for accumulating sludge separated in said chamber, the rotor also having a channel extending inwardly toward said axis and opening at its outer end into said sludge space, a stationary duct located outside the rotor, the rotor forming a connecting chamber through which said duct communicates with the inner end of said channel, pressure sensing means inserted in said duct to indicate pressure changes therein, and a pressure pulse generating means inserted in said connecting chamber and operable intermittently to induce a pressure pulse therein, said stationary duct being arranged to supply to the connecting chamber a fluid harmless to the pressure sensing means.

2. The combination according to claim 1, in which said duct conducts a gas past said sensing means and toward the rotor.

3. The combination according to claim 1, in which said pulse generating means include a second duct opening into said connecting chamber.

4. The combination according to claim 3, in which said connecting chamber is a paring chamber, said stationary ductincluding a paring device in the paring chamber, said second duct opening into the paring chamber separately from said paring device.

5. The combination according to claim 1, in which said pulse generating means include a second duct opening into said connecting chamber, the rotor being operable to maintain said connecting chamber completely filled with liquid.

References Cited UNITED STATES PATENTS 3,396,910 8/1968 Steinacker 233-20 ROBERT W. JENKINS, Primary Examiner 

